There are known in the prior art electrophotographic copying machines in which the electrostatic image to be developed is formed on a drum carrying a photoconductive surface layer. The drum is mounted for rotary movement and is driven in synchronism with a scanning mechanism to cause an electrostatic latent image of an original to be formed on the surface of the drum. In the prior art, the drum is mounted for rotary movement in bearings which are at fixed locations on the machine frame. The drive normally is provided by gearing or the like from a drive motor to the drum.
One of the defects of systems of the prior art discussed hereinabove is that of "banding" or repetitive density variations in the direction of drum rotation. These density of print changes may be the result of changes in drum speed owing to cogging of the gear drive. Another defect of such systems results from variation in the distance from an optical window in the original imaging path to the imaging portion of the drum surface such as may result from slight eccentricities of the drum or out-of-roundness thereof.
Further in operation of electrophotographic copiers of the type discussed hereinabove, the photosensitive layer may become marred or its electrostatic characteristics may become degraded after a lengthy lapse of time or the production of a very large number of copies. When this occurs to the extent that clear copies can no longer be produced, the photoreceptor drum must be taken from the machine housing and cleaned or it must be replaced by a new drum. In the arrangements of the prior art for supporting the drum in the machine cabinet, removal of the drum is a difficult operation requiring tools. Further, owing to the nature of the photoconductive layer, the drum must be very carefully handled to avoid damage to the surface thereof. Damage to other components of the machine must be avoided in removing the drum. While there are known in the prior art various expedients for mounting the drum in the machine cabinet so as to permit removal thereof, in general these arrangements are not particularly expeditious and do not solve the problems outlined hereinabove.